At some point in their education, every botany student is introduced to the ginkgo (Ginkgo biloba). I became very familiar with a huge female ginkgo tree as a freshman botany student at Ohio Wesleyan University — not in any botany class, but outside the window of my Greek literature class. That tree has since been removed, but at the time, the smell of its fruit littering the ground and crushed daily under the feet of hundreds of students filled the air with a vomit-like odor. It was cringe-worthy and memorable.
The Dinosaur Plant
Ginkgo biloba is native to Southeast Asia; it’s often called a living fossil, because it can be found in the fossil record at the same time as the dinosaurs. Ginkgoes have also remained essentially unchanged for 200 million years, and are now the only plants of their kind. They’re the only living species in their genus, family, order, and division — for comparison, all flowering plants compose another division in the plant kingdom.
Long-lived as a species, ginkgoes can also attain astonishing ages as individuals; one tree in China is estimated to be 3,500 years old. The species has had tremendous success spreading its seeds — something all plants that reproduce by seed must do to survive. Plants can’t walk, so unless they’re spreading their seeds by wind or water, they must use animals for transportation. To do so, some plants create seeds that can hitchhike in an animal’s fur; entice animals to eat delicious, seed-bearing fruit; or devise other mutually beneficial incentives. Ginkgo seeds don’t float or fly, so they must’ve been distributed by animals. However, scientists haven’t found any living creature that naturally carries, eats, or moves them. Much like the hedge apple (Maclura pomifera), the ginkgo appears to have outlived its seed dispersal partner, which may have been either a dinosaur or a prehistoric mammal. Whatever the animal partner was, ginkgoes needed a new seed dispersal strategy when it died out — and humans have enthusiastically taken the job.
Ginkgoes’ Uses as Medicine, Poison, and Food
Ginkgoes’ fleshy fruits contain urushiol, the chemical in poison ivy that causes allergic reactions and skin rashes, and the nuts contain ginkgotoxin, a chemical that disrupts the body’s uptake of vitamin B6. Ginkgotoxin poisoning occurs at about 10 nuts per day for adults and five for children — and yet, humans have used ginkgo nuts and leaves as both food and medicine for centuries.
In much of Asia, the nuts are considered a delicacy. Cuisines that feature the nuts use them in small amounts as part of seasonal side dishes or appetizers, keeping diners’ consumption of ginkgotoxin well below the danger zone. In Japan, a traditional savory egg custard called chawanmushi is made in fall to make use of fresh ginkgo nuts. The Food and Drug Administration (FDA) hasn’t approved ginkgo nut consumption as food or medicine, but if you can find a female tree, you can gather your own nuts to try. Wear gloves to protect your hands from the urushiol in the fruits, and gather them as they drop from the trees in fall. Peel and wash off the flesh, until you’re left with a woody shell resembling a pistachio. Lightly roast the nuts to make them easier to open, and remove the almond-like nut inside. Ginkgo nuts are low in calories and contain B-complex vitamins, copper, manganese, potassium, magnesium, and iron. Chinese and Japanese traditional medicine also features the nuts as anti-asthmatic, expectorants, and antitussives.
In the United States, the FDA has approved ginkgo leaves for internal use; unlike the nuts, the leaves don’t contain ginkgotoxin. Numerous clinical studies have shown the leaves to be effective at increasing peripheral blood flow and acting as peripheral vasodilators (they widen blood vessels). The active chemicals also reduce clotting, so those on blood thinners should avoid ginkgo leaf. Ginkgo leaf preparations can be used to treat brain disorders in the aged, Raynaud’s disease, and eye issues brought on by poor blood flow. Ginkgo is also featured prominently in formulas to improve memory and concentration. The leaves are high in calcium, chromium, niacin, phosphorus, selenium, and zinc, and were traditionally used in topical applications for skin disorders, though they’re now more popularly steeped for medicinal teas.
The Golden Tree
Ginkgo trees are sacred in Buddhism, and are associated with long life in many Asian folklore traditions. One of the oldest ginkgoes living today stands in the courtyard of the Gu Guanyin Buddhist Temple in the Zhongnan Mountains of China, and it’s estimated to be 1,400 years old. Each year, people make pilgrimages to be present in fall when its characteristic, fan-shaped leaves turn from green to gold and rain down to cover the courtyard. The temple monks have long cultivated and protected this tree, as their counterparts across China, Tibet, and Japan have done with their own temple trees. For hundreds of years, in fact, ginkgoes were believed to be extinct in the wild, until two groves were found near ancient monasteries in two small areas of Zhejiang province in eastern China. The International Union for the Conservation of Nature’s “Red List of Threatened Species” lists Ginkgo biloba as an endangered species because of its rarity in the wild.
Ginkgoes are near ubiquitous in human-dominated environments — so how can they be endangered? When humanity stepped in as the new propagators of ginkgoes, we were initially great partners. We’ve planted ginkgoes everywhere they’ll grow — which is almost anywhere. It turns out this lonesome species is pretty tough. In America, you’ll see ginkgoes planted along streets in subdivisions and cities, and even in the middles of parking lots. Provided with full sunlight, ginkgoes are frost hardy to Zone 3 and tolerant of dense clay or compacted soil, browsing deer, air pollution, salt spray, heat, root encroachment, and nuclear blasts. Not much survived the nuclear bomb the United States dropped on Hiroshima in 1945, but six ginkgo trees within about 2 kilometers of the blast center leafed out afterward. These resilient trees, along with other plants that re-sprouted after the bomb, are called hibakujumoku: literally “atom-bombed trees,” or in English, “survivor trees.” The problem, therefore, is not that humans haven’t planted ginkgoes in enough places; it’s that we’ve been selective in which ginkgoes we’ve planted.
Growing and Propagating Ginkgoes
Ginkgoes are dioecious, meaning there are both male and female individuals. The male trees are used frequently in plantings for leaf harvest or to decorate inhospitable places, but the female trees are often removed as soon as they reach maturity. Some suburbs prohibit the planting of female trees, while others nonchalantly recommend that any tree that offends by dropping smelly fruits be cut down. Smelly though the fruit may be, the genetic diversity it represents is essential to the health of the species. The ginkgo has been on the planet longer than humanity, but unless we start planting and valuing the female trees, too, we risk losing the species to disease or pests that can race through a largely cloned population.
I was startled to find only one seed-saving organization focused on protecting the ginkgo: Green Legacy Hiroshima carefully gathers the rancid-smelling fruits of Hiroshima’s hibakujumoku and shares them with gardens around the world in an effort to spread a dual message of caution and hope. While this group is focused on preserving the genetic line of a specific group of ginkgoes, they may well be ensuring the continuation of the species as a whole.
For my part, I planted a ginkgo tree at the center of my medicine wheel garden. I won’t know for another five years or so — when it turns 20 — whether I’ve planted a male or female. I’m so proud to be giving space to this ancient species, and the symbolism of its location is intentional as well. It’s traditional to place a peace pole at the center of a medicine wheel garden, but when we broke ground, I knew I wanted the focal point to be a living one. Today, as Green Legacy Hiroshima works to share the seeds of the ginkgoes that survived a nuclear blast, I can think of no better ambassador for the message. Perhaps the renewal of an old, mutually beneficial partnership between people and ginkgoes will allow us to look beyond the objectionable fruit and see the kernel of ancient resilience waiting to be planted in all of our gardens.
How to Save Ginkgo Seeds
- If you happen to live in a community where a female ginkgo tree grows, you can play an important part in history. Save the seeds, share them with friends, and plant ginkgoes!
- Collect the fruits when they have fallen, generally in October and November. Wear gloves to protect your hands from the urushiol in the flesh.
- Soak them to remove the shelled nut from the flesh.
- Ginkgo seeds require cold stratification in order to germinate. You can cold stratify the seeds naturally by planting them in pots and letting them sit outside through winter, or you can shorten the process by placing the seeds in moist sand and leaving them in the refrigerator for 6 to 8 weeks.
- Plant your ginkgo seeds in a moist growing medium and watch them grow!
- Ginkgo seeds will only germinate if they’ve been fertilized, and the trees are wind-pollinated. Collect the fruits from a female tree in the vicinity of a male tree (characterized by its lack of smelly fruit), and be aware of which way the wind blows!
Try ginkgo’s medicinal qualities for yourself with a fresh-brewed jug of Ginkgo Memory Tea Recipe.